There are already known various constructions of fuel cells, among them such employing a proton exchange membrane confined between respective cathode and anode electrode plates. The general principles of construction and operation of such fuel cells are so well known that they need not be discussed here in any detail. Suffice it to say that a gaseous fuel and an oxidizing gas are supplied to the anode electrode plate and to the cathode electrode plate, respectively, and distributed as uniformly as possible over the active surfaces of the respective electrode plates (that is, the electrode plate surfaces facing the proton exchange membrane, each of which is usually provided with a layer of a catalyst), and that an electrochemical reaction takes place at and between such electrode plates, with attendant formation of a product of the reaction between the fuel and oxygen (product water), release of thermal energy, creation of an electrical potential difference between the electrode plates, and travel of electric charge carriers between the electrode plates, with the thus generated electric power usually constituting the useful output of the fuel cell.
In the proton exchange membrane fuel cells of the type here consideration, each of the electrode plates typically includes a backing plate having a relatively substantial thickness and a separate relatively thin support plate that is provided with the catalyst layer at an active region of one of its major surfaces (referred to herein as the front surface) and that overlies at least a central portion of the backing plate. These backing and support plates have one thing in common, namely, that they are porous. Such porosity is needed to supply to and substantially uniformly distribute over the respective active surface the respective gaseous medium which is fed through respective channels provided in the backing plate to areas of the respective electrode plate that are spaced from the proton exchange membrane, but also to provide for removal of the reaction product (water) from one of the active surfaces and supply water to the other of the active surfaces to avoid drying out of the proton exchange membrane thereat.
It will be appreciated that, when porous elements such as the aforementioned electrode plates are used in fuel cells, it is necessary to assure that neither any liquid, nor any of the gaseous media, be able to flow out of the periphery of the respective porous element. Therefore, it is customary to accommodate the various fuel cell components in solid (fluid impermeable) frames. Furthermore, it has been proposed, in copending commonly owned U.S. applications Ser. No. 07/813,464 and/or Ser. No. 07/813,472 to make the peripheral regions of such porous fuel cell components fluid impermeable by impregnating them with respective initially flowable substances that eventually solidify in the pores of such regions to completely fill such pores.
During the operation of the proton exchange membrane fuel cell, an electrochemical reaction takes place in the fuel cell between fuel and oxygen, resulting in the generation of an electric power. This reaction is exothermic, that is, heat is released in the course of its performance. The thus released heat must be removed from the fuel cell to avoid overheating of the latter. Currently, it is customary to interpose fully sealed cooling plates at spaced locations of the fuel cell assembly or stack, and to force a cooling medium through the interiors of such cooling plates. This cooling medium, in turn, is ordinarily cooled by another coolant, in a two-stage arrangement that necessitates the use of a multitude of devices, such as pumps, accumulators, heat exchangers or the like, to accomplish the desired purpose. This makes the arrangement very complicated and expensive. Moreover, experience has shown that, when the weight of such additional equipment is taken into account, as it must be, when considering the performance of the fuel cell arrangement, the end result is that the weight per unit of electrical output is undesirably high.
Accordingly, it is a general object of the present invention to avoid the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a cooled proton exchange membrane fuel cell device which does not possess the drawbacks of the known fuel cell devices of this kind.
Still another object of the present invention is to develop the proton exchange membrane fuel cell device of the above kind in such a manner as to minimize the weight per unit of electric power generated thereby.
A concomitant object of the present invention is to devise a proton exchange membrane device with a simpler and more efficient cooling system than heretofore used in similar fuel cell devices.
It is yet another object of the present invention to design the cooled fuel cell device of the above type in such a manner as to be relatively simple in construction, inexpensive to manufacture, easy to use, and yet reliable in operation.